.TH LEFTY 1
.SH NAME
lefty \- A Programmable Graphics Editor
.SH SYNOPSIS
.B lefty
[
.I options
] [
.I file
]
.SH DESCRIPTION
.B lefty
is a two-view graphics editor for technical pictures. This editor has
no hardwired knowledge about specific picture layouts or editing operations.
Each picture is described by a program that contains functions to draw the
picture and functions to perform editing operations that are appropriate for
the specific picture. Primitive user actions, like mouse and keyboard events,
are also bound to functions in this program. Besides the graphical view of the
picture itself, the editor presents a textual view of the program that
describes the picture. Programmability and the two-view interface allow the
editor to handle a variety of pictures, but are particularly useful for
pictures used in technical contexts, e.g., graphs and trees. Also,
.B lefty
can communicate with other processes. This feature allows it to use existing
tools to compute specific picture layouts and allows external processes to use
the editor as a front end to display their data structures graphically.
.SH USAGE
The file name is optional. It may be
.BR - ,
for reading from standard input.
.B lefty
uses two environment variables,
.B LEFTYPATH
and
.BR LEFTYOPTIONS .
.B LEFTYPATH
is a colon separated list of directories. When
.B lefty
tries to open a file, it searches that path for the file. When
.B lefty
tries to start up another process, it searches
.B LEFTYPATH
first, then the standard
.B PATH
variable.
.B LEFTYOPTIONS
can be used to set specific options. Options specified on the command line
override options set through this variable.
.SH OPTIONS
.TP
.B -x
Instructs the editor to exit after processing
.BR file .
.TP
.B "-e <expression>"
.B <expression>
is parsed and executed.
.TP
.B -el <num>
Set error reporting level. The default value is
.BR 0 .
.B 0
never prints any messages.
.B 1
prints severe errors, such as trying to return from a non function.
.B 2
is the most useful: it reports function calls that cannot be executed, either
because there is no function, or because of argument mismatches.
.B 3
also warns about bad variable names.
.B 4,5
warn about expressions that do not return a value. Only level
.B 1
messages are real errors. The rest arise from legal
.B lefty
statements, but may be cased by some logic errors.
.TP
.B "-sd <num>"
Specifies how much of the stack to show, when an error message is to be
printed. The default value is
.BR 2 .
With
.BR 0 ,
no part of the stack is shown. With
.BR 1 ,
only the top stack frame is printed. With
.BR 2 ,
the full stack is printed.
.TP
.B "-sb <num>"
Specifies how much of each function in the stack to show, when an error message
is to be printed. The default value is
.BR 2 .
With
.BR 0 ,
no part of the function is shown. With
.BR 1 ,
only the line around the error is printed. With
.BR 2 ,
the full function body is printed.
.TP
.B "-df <string>"
Sets the default font. This font is used whenever a requested font cannot be
found. The string must be a legal X font. If string is
.BR "''" ,
.B lefty
will draw small boxes instead of text.
.TP
.B "-ps <file>"
Specifies a default file name for postscript files. This name is used when no
name is specified in the
.B createwidget
call. The default file name is
.BR out.ps .
.TP
.B -V
Prints the version.
.SH SEE ALSO
.I lefty
user guide.
